1. Field of the Invention
In the use of turbocompressors, whether they be radial or axial, it is attempted for the sake of high reliability during partial load operation to achieve stable characteristics falling monotonously with increasing throughput without hysteresis. However, stable characteristics are the more difficult to achieve under partial load, the higher the pressure ratio at the design point becomes. Attempts are made to remedy this in practice; to achieve the desired characteristics by additional stabilization devices. Due to differences in the design of the blades and in the structures of the regions of change from laminar to turbulent flow during partial load operation, no clear technical solution has hitherto crystallized out, according to which a general handy stabilization device could be derived.
It is therefore impossible to say at present with scientific precision whether a stable characteristic can be achieved at all, and with what stabilization device, in a given compressor. This unsatisfactory situation is experienced particularly in the case of radial compressors.
2. Discussion of Background
A stabilization device in a radial compressor, which has become known from EP-A No. 1-0,229,519, possesses the feature that the inner housing, as the jacket of the impeller, exhibits radial or quasi radial bores. Said bores establish a connection between approach flow duct and blading, being masked more or less on the blade side by the blades. Although such bores shift the pumping limit and stability limit in the characteristic, they do so at the cost of high losses of efficiency which may amount to 4-5 per cent. It is substantially impossible by this proposed solution to achieve the desired extension of performance at small throughputs which would be necessary due to the instabilities which occur for a specific mode of operation. Another significant factor here is that this minimal stabilization effect has to be obtained at the cost of a disproportionately high loss of efficiency.